Control apparatus



March 31, 1942.

c. E. MASON CONTROL APPARATUS Original Filed July 31, 1955 8 Sheets-Sheet 1 INVENTOR Clesson E. Mason way, an, 9M f ATTOR March 31,1942. 7 c, A N 2,277,768

' -CONTROL APPARATUS Original Filed July 31, 1935 8 Sheets-Sheet 2 March 31, 1942. c, E, ASON 2,277,768

CONTROL APPARATUS Original Filed July 51, 1935 8 Sheets- Sheet 5 INVENTOR Gleason E. Mason March 31, 1942. I Q MASON 7 2,277,768

- CONTROL APPARATUS Original Filed July 31, 1935 8 Sheets-Sheet v4 INVENTOR Clesson E. Mason BY ATTdRNEYs March 31, 1942;

c. E. MASON CONTROL APPARATUS Original Filed July 31, 1935 8 Sheets-Sheet 5 INVENTOR 4 Mason, ATTORNEYSA/ L'ING RANGE THROTTLINQ RANGE LEVEL CHANG r m n H n CZesson E. 0% r SETTING RANqE C. E. MASON I CONTROL APPARATUS March 31, 1942.

Original Filed July 31, 1935 8 Sheets-Sheet 6 w@ M m DTW mE m m .fi WM M 1p Cm March 31, 1942.

c. E. MASON CONTROL APPARATUS Original Filed July 31, 1935 8 Sheets-Sheet 7 lNVENTOR Clesson Mason ATTORN March 31, 1942. c. E. MASON CONTROL APPARATUS Original Filed July 31, 1935 8 Sheets-Sheet 8 INVENTOR Clesson E. Mason Patented Mar. 31, 1942 CONTROL APPARATUS ,Clesson E. Mason, Foxboro, Mass., assignor to The Foxboro Company, Foxboro, Mass., a cor poration of Massachusetts Original application July 31, 1935, Serial No.

34,111, now Patent No. 2,216,039, dated September 24, 1940. Divided and this application August 25, 1938, Serial No. 226,622

8 Claims.

This invention relates to control apparatus and V in its more specific aspects to apparatus responding to the value or values of a variable condition to regulate a second condition which influences the first condition, and to an instrument incorporated in such an apparatus, which functions in accordance with the first or variable condition to initiate control effects on a force or forces regulating the influencing condition. An example of one use of such control apparatus and incorporated instrument is in the field of the control of the flow of liquid from a container in accordance with the level of liquid in the container (wherein the level of liquid represents the first or variable condition and the flow of liquid from'th container the second or influencing condition) either to maintain the level substantially constant or to maintain the flow substantially constant but variable within limits in response to change of the liquid level to keep the liquid level within the limits. Control apparatus so applied forms the subject matter of-my Patent No. 2,216,039, issued September 24, 1940, of which the present application is a division.

The present invention further contemplates. the provision of an instrument containing special provision for widely varying its throttling range so that when the throttling range is narrowed it 'may vary the influencing condition to maintain the first condition substantially constant, or so that when the throttling range is widened the instrument maintains the influencing condition substantially constant but varying sufiiciently as always to keep the first conditionwithin limits. When the control instrument is adjusted to the control as last described, additional provision is made automatically to narrow the throttling range at the predetermined limits of the first condition to make sufliciently large corrections to the second or influencing condition as to keep the first condition from varying beyond the predetermined limits. The term throttling range as herein used refcrs to the change that a unit change in the value of the first condition produces in the second or influencing condition. Thus, with a narrow throttling range, the unit change of the second or influencing condition produced by a unit change of the value of the first crndition would be large. With a wide throttling range the same unit change of value of the first condition would produce a much smaller change in the second or influencing condition.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts as will be exemplified in the structure to be hereinafter described and the scope of the application of which will be indicated in the following claims.

In theaccom'panying drawings, in which are shown one or more of the various possible embodiments of this invention,

Figure 1 shows in vertical section a housing for a ball float (shown in elevation) for indicating the liquid level in a, tank, such operating the control mechanism of the present invention;

Figure 2 is a front elevation of the exterior of the casing containing the control mechanism;

Figure 3 is a right side elevation of the casing;

Figure 4 is an enlarged vertical section taken through line 4-4 of Figure 1 showing in vertical section parts of the" control mechanism;

Figure '5 is a diagrammatic flow sheet of the pneumatic control system operated by the control mechanism;

. Figure 6 is a detail view of a distributor link of the mechanism shown in Figure 7 Figure 7 is an enlarged front elevation of the control apparatus in the casing shown in Figure 2, the cover being removed;

Figure 8 is a horizontal section taken on the line B8 of Figure 7 Figure 9 is a detail of a slidable connecting clip;

Figure 10 is a vertical section taken on line |0l0 of Figure 7;

Figure 11 is a section taken on line H-H of Figure 10;

Figure 12 is a section taken on line l2-l2 of Figure 10;

'Figure 13 is a section taken on line |3l3 of Figure 7; g

Figure 14 is a section taken on line 14-44 of Figure 7;

Figure 15 is a view showing linkage mechanism of apparatus shown in Figure '7 with other parts omitted;

Figures 16, 17 and 18 are views similar to Figure 15 showing the parts in difierent positions;

Figure 19 is a section on line l9-I 9 of Figure 7;

Figure 20 shows how the mechanism may be adjusted to change the control from wide throtat I!) a, tank such as might be used in an industrial process. Liquid flows to the tank through a pipe (not shown). A valve i2 in line H regulates the flow of material from the tank.

In the present embodiment the liquid level is measured by a ball float I4 mounted in a float chamber l5 connected with the tank through pipes l6 and H. The position of the ball float is determined by the liquid level in the tank and is transmitted to control mechanism forming the subject matter of the present application, such being contained in a casing generally indicated at l8 which control mechanism through a pneumatic system operates a diaphragm motor generally indicated at 19 which operates the edge, is a resilient connecting link 38. The link is bent so that its other end may be secured by suitable screws to a split block 31 provided with a hole 38, the axis of which is approximately coincident with a line containing the knife edge. Block 31 is secured to a shaft 40 (by clamping screw 39) freely supported in a pressure-tight bearing generally indicated at 4|, which in the present embodiment includes an outer supporting casing 42 having a bore 42a and threadably mounted in a block 2|a secured to casing 2i. The casing 42 carries at its right end a bushing 43 forced into the bore 42a. At

the left end the bore 42a is provided with a valve l2. The control mechanism employs the principles described in my United States Patent No. 1,897,135, issued February 14, 1933.

It is desirable to have the control mechanism immediately responsive to minute changes in the liquid level, and to this end the entire mechanism should be free from such frictional resistance as would prevent it from responding to movement of the ball float or would prevent the ball float from responding to movement of the liquid level. It is often desirable in controlling liquid level either to have a relatively wide throttling range so that the liquid level may be permitted to vary considerably without changing the flow appreciably, or a narrow throttling range wherein the level would be maintained substantially constant but the flow would be varied widely to maintain the level constant. These desirable features are accomplished in the present invention.

Referring to Figure 1, the ball float mechanism whole is mounted in the float chamber and a casing formed by sections 2| and 22 suitably held together by bolts and gaskets to provide a. fluid tight structure. Rack 23 is cut out to receive a hardened notched supporting member 24. ,Adjustable counterweights 21 are carried by rod 26.

This assembly is supported'by a knife edge 28 (Figure 4) mounted on a shelf 29 extending into the casing from a cover plate 30. Projecting downwardly from the sides of the rack are guide plates 9 suitably held in place by screws 8 to keep the-rack from inadvertently sliding out of position with respect to the knife. The edge of the knife 28 sitting in the notched member 24 provides a pivotal frictionless support for the float assembly, the ball l4 being free to change its position with slight changes in the liquid level.

As shown, a swing of 30 (15. either side of the normal level) is permitted. The counterweights 21 may be adjusted along the rod 25 to adapt the float to liquids of varying specific gravities.

To aid in shipping of the instrument the lower inside surface of the rack 23 is notched as shown at 32.- Before shipping, a bolt 33 is threaded up to clamp the rack 23 against the lower edges of the shelf 23 which are so constructed as to mesh with notches 32. Bolt 33 is covered by cap 34 so that when the bolt is withdrawn from clamping position after the apparatus has been installed the assembly may be made leak-proof by tightening the cover cap 34.

Referring to Figure 4, mechanism for transmitting the rotational movement: of the ball float to the control mechanism is shown. Secured to the top of rack 23 and positioned in a groove 35 extending across the rack parallel with the knife bushing 44 suitably held in place. The shaft 40 is preferably of a hardened material accurately machined as are the bushings. The bore of the bushing 43 is preferably machined to the same diameter as the shaft. The bushing 44 is provided with a bore to give the usual clearance between it and the shaft 40. The shaft 40 is slipped through bushing 44 and ground into bushing 43 with a suitable grinding operation so that the clearance between the shaft and bushing is very small. A lubricating film is maintained between the shaft and bushing by forcing lubricant under pressure through a passage 45 communicating with the interior of the casing 42. The small clearance between the shaft and bushing 43 prevents undesirable flow of the lubricant from the right end of the bearing assembly, The process pressure is usually suflicient to prevent flow from the left end.

As shown in Figure 4, the pressure bearing assembly extends forwardly through the back of housing 1 in which the control mechanism is located and to which the ball float mechanism casing is suitably bolted. Mounted on shaft 40 is a split block 41 which is clamped to the shaft by tightening a screw 4|a in the block. The back side of the block has acurved, convex surface for providing a suitable contact with bushing 43 to limit the axial movement of shaft 43 in one direction. The axial movement of shaft 40 is limited in the other direction by means of a jewel bearing stop 45a, adjustably mounted on arm 46.8,i1Dp0rted by sleeves 46a and bolts 48b and a supporting member 460. The supporting member 460 is supported by and locked to the casing 42 by a nut 46d threaded on to the casing. The adjustments are preferably made to allow slight axial play of the shaft 40.

The axes of the various parts making up the pressure-tight hearing are coincident with a line containing the knife edge 23 so that as the ball K float pivots about the knife edge its rotational movement is transmitted to the split block 41 without creating any undesirable pressure between the parts that would produce undesirable friction. The resilient connection 38 between the float and shaft furthers the assurance against -float assembly is transmitted through the resillent member 33 and the shaft 43 (so mounted that undesirable friction is eliminated) to the block 41.

Control mechanism As above mentioned the measurements made by the liquid level mechanism are transmitted to a control mechanism of the present application which through motor 19 positions valve l2. The principles employed in the control mechanism are described inthe above mentioned Patent No. 1,897,135 and only a brief description of the pneumatic system and general operation will be described here.

Referring to Figure 5, there is generally indicating at its other end with the atmosphere. The

passage 56 also connects with a port 51a and supports a double headed valve 51. In its extreme right position valve 57 closes passage 56 from the atmosphere and in its extreme left position opens the passage to the atmosphere but completely closes it from chamber 54. Port 51a is connected by pipe 58 to diaphragm motor I9. Thus when the valve is in the extreme left position the diaphragm motor is connected with the atmosphere and'when the valve is in its extreme right position the diaphragm motor is connected with the chamber 54 and full line pressure in port 52. Thus, by suitable operation of the instrument, as will be described, thepressure on the diaphrams motor may be varied from zero to the maximum pressure in the supply line.

The valve 51 is positioned by the bellows 59 which expand to move the valve to the right .with increasing pressure, and collapse to move the valve to the left with decreasing pressure. The pressure in the bellows is controlled by a pneumatic control couple comprising a nozzle 60 and flapper 6|. Nozzle 60 is connected to the supply Mounting the nozzle 60 on, the bellows 65 provides for a continuous rapid vibration of the nozzle and of the value of thepressure in the bellows 64. The pressure vibration thus created in the bellows 65 is transmitted to other parts of the air system and particularly to the bellows 59 and serves to reduce undesirable effects of friction which may be in the mechanical partsv oi the air system. g

The relative position between the nozzle and the flapper varies as described in Patent No. 1,897,135. Thecontrol mechanism shown in Figure 7 is adapted to accomplish this. Referring again to the diagrammatic flow sheet (Figure and Figure 19', flapper BI is held against a stop screw by a hair spring Bla. The screw is adjustably mounted in a pivoted lever 1 l which is positioned through mechanism not shown in the flow sheet by element I00 attached to block M and shaft, which are rotated by the ball float, and by a rack 13. The rack 13 is mounted between opposing bellows and 15. When equal pressures exist in the bellows, therack assumes a neutral position, but if the bellows 14 has a pressure within higher than the pressure in bel- .lows 15, the rack is, shifted to the right an amount corresponding to the pressure difference. If bellows 15 has a pressure within higher than the pressure in bellows M, the rack is shifted to the left of neutral position an amount corresponding to the pressure diiference. The movements of the condition-sensitive element I00 and the rack 13, through the linkage mechanism, are algebraically added and the sum of the movements is transmitted to lever II and to the flap- Q As shown in the present embodiment bellows port 52 by pipe 62; having a restricting tube 63' to regulate the flow of gas to the nozzle. The

nozzle is mounted on a bellows 64 connected to the pressure in the pipe 62'. The pressure in the line 62 is varied by the relative positions of the nozzle and flapper 6|.

When the flapper covers the nozzle opening,

a maximum back pressure starts building up in the line 62 and bellows 59. When the flapper is moved away from the nozzle 60, the pressure in the line 62 and bellows 59 starts decreasing. When the flapper BI is moved away from the nozzle beyond a certain limited distance, the back pressure in line 82 and bellows 59 decreases to a certain minimum back pressure. For various intermediate relative positions of the nozzle and flapper, the back pressure in line 62 and bellows 59 balances to various values intermediate the maximum and minimum back pressures.

In the present embodiment when the flapper and nozzle are separated beyond approximately a thousandth of an inch, the back pressure in line 62 and bellows 59 decreases to the minimum back pressure above referred to. Thus the range of movement of the flapper with respect to the nozzle, for establishing the said intermediate back pressures, is approximately one thousandth of an inch. Further, these intermediate back pressures bear only an approximately proportional relationship to the intermediate relative positions of the nozzle and flapper within this thousandth of I an inch range.

in the control head 5| which port also communicates with pipe 58 and the diaphragm motor.

Thus, the pressure in bellows 14 is the same as that existing in the diaphragm motor.

Bellows l5 and bellows 14 are connected by means of tubing contained in a housing 18. The

tubing has a capillary bore and serves to restrict the flow of gas from or to bellows 15 so that changes in pressure in the bellows 14 due to changes in position of the valve 51 only gradually are transmittedto the bellows 15 as the equalizing pressure seeps through the capillary tubing. Several lines of capillary tubing are usually provided so that more or less capillary tubing can be inserted between the bellows l4 and 15, depending upon the nature of the process being controlled} As shown in Figure 7, the capillary tubes have leads 18a which may be connected with one another through suitable couplings. Referring to Fig. 7, the leads coming from the extra capillary tubes are shown at 18b, and these leads terminate in connecting collars 18c which, for purposes of convenience, are secured by screws 18d to a plate 18c. If it is desired to connect'either one or both of the'extra capillary tubes across the bellows l4, 15, the connecting collars are removed from the plate Ne and secured (as shown in Fig. 5) to the stack of collars shown at 18) to connect the additional tubes in series with those already in the system. Varying relative pressures in the bellows 14 and 15 position the rack I3 as described in Patent No. 1,897,135.

Connected to line 1-1 and 18a by means of piping or tubing 11b is a chamber 1111. This chamber gives additional capacity to. the bellows 15 when needed. Increasing th capacity of the .4. bellows 15 has the effect of slowing down the rate at which it tends to return the process the instrument is controlling to the control point.

The linkage for transmitting to the flapper the motions of the condition-sensitive element and changes in the position of the rack without undesirable frictional resistance or lost motion is shown in Figures '1 through 18.

Referring more particularly to Figures 6 and '1, on block 41 is mounted a distributing link I having a'hole for receiving the end of'shaft 40, and a curved slot IIlI provided with an enlarged cut out portion as shown in Figure 6. A screw I02 threaded into blcck 41 clamps the distributing link in place. The screw has a shoulder I03 which meshes with the enlarged part of the slot to align the link with the blcck. Thus the link assumes positions corresponding to position of the ball float. Axis A coincident with the axis of shaft 40 forms one fixed fulcrum' of the lever mechanism. Another fixed point of the lever mechanism is shown at B (Figures '1 and about which point a frame, generally indicated at I05 (Figure 8) is pivoted. The frame comprises an outer plate I06 and an inner plate I01 held together by spacing sleeves I08 and screws I09. The frame is suitably pivoted between two arms III] and III, the arm III being secured to the back of the casing 1 by a screw and a projection II2 extending into a hole in the back of the casing.

A third fixed fulcrum of the lever mechanism is shown at C about which the flapper operating lever 1I pivots.

Main movable or adjustable fulcrum points are also provided in the mechanism, one of them generally indicated at D is mounted on the frame I05. The other generally indicated at E is mounted on rack 13 supported by bellows 14 and The distributing link I00 has four arms (Figures 6 and '1) H3, H4, H5 and H6. Arm II5, which extends generally parallel to a line passing between points D and B when the control point is substantially central, is connected by means of a resilient link II1 with one arm II8 of a bell crank (Figure 8) comprising the arm II8, a shaft H9 and an arm I20, The arms H8 and I are securely attached to the shaft II9 which is mounted between the plates I06 and I01 of frame I05. The link II1 although normally of a predetermined length is made resiliently contractable so that in the event of unusual movement of the distributing link I00 undue strain will not be placed on the mechanism but will be absorbed by the resiliency of the link II1.

Pivotal movement of link I00. is thus transmitted to arm I20. Linked to arm I20 by means of connecting link I2I is another bell crank (Figure '7 and lower right-hand corner of Figure 4) comprising arm I22, spindle I23 and arm I24, the arms I22 and I24 being rigidly secured to the spindle I23 which is mounted between arms I25 and I26 of the rack supported by the bellows. Thus movement of the arm I20 is transmitted to arm I24.

Connected to arm I24 by means of connecting link I21 is another bell crank comprising a double ended arm I28, shaft I29 (Figure 10), and arm I30, arms I28 and I30 being secured to the shaft which is pivotally mounted between supporting bars I3I and I32, which bars are rigidly spaced from one another by means of spacing sleeves I33 and held togetherby screws I34. A

aermee screw I35 serves to mount bar 532 on the back of the casing and a projection I36 accurately aligns the bar with the casing. It is noted that the axis of the shaft I29 is coincident with the fixed fulcrum point C.

With the linkage as described pivotal movement of shaft 40 and. distributing link I00 is transmitted to bell crank arm I30.

By the mechanism shown in Figures 10, 11, 12, 13 and 14, the motion of hell crank arm I30 is resiliently transmitted to the long lever II freely mounted on spindle shaft I29 by means of a-lever I31 also freely supported on the spindle I29 and having an inwardly projecting lug I 38.

Arm I30 is resiliently held against the inwardly projecting lug I38 by means of a light coil spring I40 and lever H is resiliently held against the outwardly projecting lug I39 by means of light coil spring I4I. Thus movement of lever I30 clockwise positively drives lever I31 through the lug I38 but only resiliently drives lever 1I through spring I4I. Movement of lever I30 counterclockwise resiliently pulls lever I31 in the same direction which positively drives lever H in the same direction. Lever 1I however is free to move about the spindle I29 in either clockwise or counterclockwise direction without moving arm I30.

Thus the lever H is mechanically though resiliently linked to the shaft 40 and to the rack 13, As shown in Figures 7 and 15 through 18, the linkage mechanism is so adjusted that a relatively large movement of the shaft 40 and distributing link I00 produces only a relatively small movement of the arm I 22. Thus, an appreciable change in the liquid level in the container would cause only a relatively small correction to be made by the control mechanism to the setting of the valve motor I9.

When the above described mechanism is in operation, any movement of the flapper produced by movement of the ball float, acting through the distributing link I00, which would tend to cover or uncover nozzle 60 affects the pressure in throttling bellows 14 to move the rack 13 and point E to cause a follow-up movement of the flapper. This primary reaction is such that the quantity change in pressure in bellows 14 is proportional to the change in the ball float posiion. 7

In addition to this primary reaction" there is a secondary reaction produced by the reset bellows 15. Bellows 15 opposes bellows 14 and has a pressure connection with bellows 14 through the capillary tubing 10. Thus so long as a differential in pressure exists between the bellows 14 and the bellows 15 the seepage of the air from one bellows to the other produces a rate of change of pressure in the bellows 14 which varies with the difference of the pressures. Thus for any given resistance 18 in the connection between the two bellows a given pressure difference will produce a given rate of change in the bellows 14.

When equal pressures exist in the two bellows they hold the rack and point E in a neutral position, and this position requires a substantially definite position of the ball float to maintain the linkage mechanism in such position as to hold the flapper within operating range of the nozzle. The liquid level required to hold the ball float in this position is called the control point at which the instrument is adjusted to maintain the liquid level.

The primary reaction tends to produce decreased pressure in the bellows 14 when the ball float is below the control point, whereas a positive rate of level change produces a positive rate of pressure change in thebellows I4. The secondary reaction tends to produce a positive rate of change for a deviation of the ball float above the control point. secondary reactions together will cause the actual pressure in bellows It to be the algebraic sum of these two effects. The pressure in bellows I4 may be increasing, decreasing, or standing still, dependent on the rateof change of the level at certain deviations and will always have zero rate of change when the control point is reached. Since it is desirable that any changes in the rate of flow from the tank I should behave in accordance with the same general characteristics as the pressure in bellows I4, the pressure in bellows I4 is used as the operating pressure of the valve motor I9,

As explained above, any equal pressures from zero to a. full supply of pressure may exist in the bellows 14 and I5 when the rack I3 is in its neutral position and the ball float at its control point. I

As described above, an instrument set-up as shown in the drawings has a wide throttling range so that a rising liquid level produces only a relatively small corresponding increasing of the pressure in bellows I4. The instrument thus adjusted can be used for maintaining the flow from the container approximately constant, i. e., without wide variations or surges in the flow in Therefore the primary and line II, while at the same time always correcting the flow in the direction to correct for variations in the liquid level. v

The control point at which the level is maintained or at which the instrument is set to maintain the level is manually adjustable'by shifting the position of the fulcrum D. To this end (Figures 7 and 8), frame I05 may be pivoted about the pivotal support to shift bodily the fulcrum of bell crank H8, H9, I20. The shifting of the frame is accomplished through a connecting link I42 attached at one end to outer plate I06 and at the other end to a crank arm I43 secured to a bevel gear wheel I46 carried on a'shaft I45 mounted on a frame I46 suitably supported on pivot point lever I61 which, by means of a wire link I68, is connected to arm II4 of distributing link I00.

As shown in Figure 'I, the various links and connections are preferably so related and proportioned with respect to each other that when the control point is in the middle of the operative control range of the instrument, the pivot point between the connection III and the bell crank arm H8 is coincident with the axis B so that adjustment of the control point above or below the mid-position produces a minimum angular change in the linkage mechanism and connections and so that such change as is produced by such adjustment is the same whether the control point he set up or down. In the midposition of adjustment, too, it is preferable that the angle formed between the respective arms H5 and H8 and their connecting link III be.

substantially 90 so that a unit rise or fall of the liquid level produces the same motion of the bell crank II8--I20.

The linkage'mechanism as shown in Figure 7.

for transmitting movement of the'shaft 40 and movement of the rack I3 to the flapper is preferably free from frictional resistance and lost motion. In the present embodiment this is accomplished by having the bell cranks and the shaft I29 loosely mounted in their respective supports and by having the connections between the connecting links-and the bell cranks also free and loose. Thus, friction is reduced to a point where it does not interfere with the movement of the parts.

The linkage also is free from lost motion. The parts are light in weight and hang on their respective supports which are all concave curved surfaces that always center the parts in the same centers. Thus there is no side play such as would introduce lost motion.

The rack 13 supported between the two spring bellows also moves without any frictional resistance.

the wall of the casing. Rotation of gear I44 to swing crank I43 to shift the position of frame I05 is accomplished by turning a knurled knob I 61 extending from a shaft I48 to the outside of the casing. The inner end of the shaft carries a worm gear I49 for driving gear I44.

The position of frame I05 and of the point at which the 'mechanism is set to maintain the liquid level is indicated by means of a pointer I50. Referring to Figures 7, 8 and 15, pointer I 1 I50 is mounted upon a U-shaft I which swings from supporting arms I53, I54. These support-.

ing arms are carried by posts I 5| which posts have a foot secured by screws I5Ia to the back of the instrument casing.

The front leg of the U-shaft I60 is adjustably connected with the pointer I50 by means of an adjusting screw I6I.

Secured to the other leg of the U-shaft I60 and in properly adjusted relationship with respect thereto, is a lever I62 connected by means of a wire link I63 with a raised projection I64 'v extending from the outer plate of frame I05.

The position of the ball float and shaft 40 and distributing link I00 is indicated by pointer I65 rigidly secured to a U-shaft I66 which is pivotally swung from supporting plates I52, I55. To the inner leg of the U-shaft I60 is secured, in properly adjusted position with reference thereto, the

Different positions of the linkage mechanism are shown in Figures 15 through 18. In Figure 15, the linkage is shown (as in Figure 7) with the control point set substantially in the center. The liquid level also is at the desired level as indicated by pointer I65 overlying pointer I50. Preferably when in this position the arms I20 and I22 of the bell cranks are parallel and the connecting link I2I is perpendicular to arms I20 and I22 so that movement of the distributing link I00 clockwise or counterclockwise, produces equal movement of 'the arms I20 and I22 in each direction.

' To these ends numerous assembly adjustments 'of the linkage mechanism are provided to compensatefor manufacturing tolerances. The link I2I is preferably formed of two parts suitably joined (Figure 7) by screws I 2Ia positioned in slots I2Ib so that the length of the link may be tal. This is a factory assembly adjustment made by positioning block 41 about shaft 40 in such manner that when distributing link I00 is properly mounted on block 41 (see Figure 6) the dis-,

tributing link is horizontal. Another assembly after being made.

adjustment is provided by making the length of link I21 adjustable by forming it in. two parts held together by screws I210. so that the position of the bell crank I28, I29, I30 may be adjusted independently of the movement of arms I20 and I22. This adjustment, too, is soldered A fine-adjustment between lever H and the flapper is provided by the adjustable stop screw 10.

In Figure 16 the position of the parts is shown with the control point shifted to maintain a liquid level above that which would be maintained by the position of the parts as shown in Figure l5when the instrument is assembled as shown in Figure 1.

Figure18 shows the position of the parts when the control point is set as shown in Figure 15 but with the liquid level above the desired level, thereby causing the distributing link I to be rotated clockwise, and arms I20 and I22 to be lowered to move the arm I24 counterclockwise. This, as above described, tends to uncover nozzle 60, so that the pressurein bellows 14 is increased to move rack 13 to the right to maintain the flapper tangent to the nozzle. The increased pressure opens the valve further and as the liquid level moves back toward the control point, the pointer I65 moves back toward the central control point position of pointer I50.

When a tank isinserted in a process to absorb surges in flow, the liquid level controller used in connection with the tank is adjusted to have a reasonably wide throttling range so that surges in the flow into the tank are absorbed and the flow out is made more uniform. To this end the mechanical advantage of the linkage as shown in the drawings is such that deviation of the liquid level from the control point produces only arelatively small movement of arm I24 and a consequent relatively small proportional change of pressure in bellows 14 and consequent movement of rack .13 to keep the flapper GI tangent to the nozzle 60.

. But in instances where a tank is so used as to require a substantially constant liquid level, it is desirable to adjust the controller to give it a narrower throttling range so the same deviation of the ball float will cause much larger proportional change in pressure in bellows 14, to keep the nozzle and fiapper'tangent. To accomplish the change in adjustment as shown in Figure 1, the connecting link I2I is adjustably connected to arms'l20 and I22 by means of 'a spring clip arrangement shown in Figure 9 wherein. a spring I2Ic is adapted to engage notches I2Id positioned along the bottom edges of the arms I20 and I22. Movement of the link I2I to the right along the arms I20 and I22 decreases the throttling range. The throttling range may also be changed by shifting the position of link I21 with respect to arm I24.

Although it is desirable to have a fairly wide nected by means of a link I18 to the upper arm- II3 of the distributing link I00. The other arm I carries at its outer end an extension I19 adjustably secured to the arm I16 by screws I80. The extension I19 carries at its end a yoke member having depending sides I8I and I82 between which lies the upper end of lever 1I. Movement of shaft and distributing link I00 pivots the extension member I19 about the axis I29 independently of the movement of the bell crank arms I20 and I22. Movement of shaft 40 moves extension I19 much farther than lever 1| is moved by the same movement of shaft 40. With this mechanism when the liquid level reaches predetermined limits, the yoke member overtakes the lever H and moves it independently of movement of the arms I20 and I22.

Figure 20 shows the the range in which it may be desirable to have the yoke member, which serves as the fast-throttling safety device, come into effect. Figure 17 shows the position of the mechanism when the shaft and its associated parts have moved sufflciently far to bring the safety device into operation. The safety device in effect changes the control instrument as shown in Figure 20 from a relatively wide throttling to a very narrow or fast-throttling control. The levels at which it is desired to have the safety device take effect may be adjusted by lengthening or shortening the arm'made up of arms I16 and I19. The longer the arm the narrower is the fast-throttling range and the sooner the safety device overtakes lever II and narrows the wide-throttling range. Shortening of the arm produces the opposite effect.

In the event that it is desiredto reverse the control action of the control apparatus or to change the position of the instrument case to the opposite side of the ball float mechanism from that shown in Figure 1, provision is made to shift the position of the link I21 to the upper end of arm I28 and to shift the link I18 to arm II6 of distributing link I00. In addition it is necessary to reverse the connections from the equalizing valve and to connect the control head to bellows 15 instead of to bellows 14.

Reviewing the operation of the instrument as described, the ball float I4 in Fig. 1 measures the level I3 existing in the tank I0 and transfers this measurement to the distributor link I00 shown in Fig. '1. The distributor link I00 through the amplifying system adjusts the air pressure going to the valve motor I9 to tend tokeep the level I3 at a predetermined value called the control point. The amplifying system includes what might be termed two pilot valves (a primary pilot valve 60, GI, and a secondary pilot valve 53). Through linkage mechanism the distributor link I00 operates the pilot valve in conjunction with a pneumatic motor (bellows 14), which pneumatic motor accomplishes this amplification by always keeping flapper GI within its operating range with respect to the nozzle 50 regardless of the position of the distributor link I 00. The pneumatic motor (bellows 15) opposing the action of the bellows 14 returns the axis E to a neutral point (when the pressures in the bellows 14 and I5 are the same). Thus the control apparatus can never come to a. condition of equilibrium so long as the ball float is away from the control point, because only at the control point exist in the bellows I4 and 15. And, as described above, unless the flapper is within the operating range with respect to the nozzle, the instrument tends to supply maximum or minimum pressure to the valve motor I9. An instrument embodying the linkage mechanism shown in this type of control instrument, is more flexible in its adaptation to difierent processes. It may be adjusted to have a wide or narrow throttling range without producing other undesirable or unequal changes in the operation of the instrument. Fur ther, the relationship between the air pressure supplied to the valve and the value of the condition is readily adjustable also without introducing unequal operating conditions into the instrument.

As many changes could be made in carrying out the above constructions without departing from the scope of the invention, itis intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and-not in a limiting sense. I 1

I claim: I

1. Means for establishing a pneumatic control pressure responsive to a variable condition comprising, in combination, condition-responsive means, a pilot valve, valve mean responsive to the operation of said pilot valve for controlling the supply and waste of air from a source to establish said pneumatic control pressure, a pneumatic motor operated by said pneumatic control pressure, linkage mechanism including a first lever pivoted about an adjustable axis and operated by said condition-responsive means, a second lever pivoted solely about an axis movable by said pneumatic motor, a connecting link for transmitting motion of said first lever to said second lever, and an operating link for operating said pilot valve from said second lever, whereby ated by said condition-responsive means, a second lever pivoted solely about an axis carried by .and movable by said pneumatic motor, a connecting linkfor transmitting motion of said first lever to said second lever,- and an operating link for operating said pilot valve from said second lever, one of said links being adjustable witliIespect to one of said levers to change the mechanicaladvantage between the link and the lever without affecting'the angularitybetween the link and the lever to adjust the amount of change in said pneumatic control pressure caused by a unit change of the condition-responsive means, and

means for adjusting the position of the first axis do adjust the relationship between said first axis and said condition-responsive means.

4. Means for establishing a pneumatic control pressure responsive to a variable control condition comprising, in combination, condition-'remechanism for interconnecting the movement of movement of said condition-responsive means" and said pneumatic motor each operates said pilot valve to cause said pneumatic control pressure to change in accordance with movement of the condition-responsive.means.

2. Means for establishing a pneumatic control pressure responsive to a variable condition comprising, in combination, condition-responsive means, a pilot valve, valve means responsive to the operation of said pilot valve for controlling the supply and waste of air from a source to establish said pneumatic controlpressure, a pneumatic motor operated by said pneumatic control pressure, linkage mechanism including a first lever pivoted about an adjustable axis and operated by said condition-responsive means, a second lever pivoted solely about an axis movable by said pneumatic motor, a connecting link for transmitting motion of said first lever to said second lever, and an operating link for operating said pilot valve from said second lever, whereby movement of said condition-responsive means and said pneumatic motor each operates said pilot valve, and said connecting link being adjustable with respect to said levers to change the mechanical advantage between the levers without changing the effective angularity between them to adjust the amount of change in said pneumatic control pressure caused by a unit change of the condition-responsive means. 7

3. Means for establishing a pneumatic control pressure responsive to a variable condition comprising, in combination, condition-responsive means, a pilot valve, valve means responsive to the operation of said pilot valve for controlling the supply and waste of air from a source to establish said pneumatic control pressure, a pneumatic motor operated by said pneumatic control said condition-responsive means and said bellows to move said flapper, said linkage mechanism including a first lever pivotable about a manually adjustable axis, a second lever pivotable about' an axis carried by said bellows and movable thereby, a link connecting said first and second levers, a link operatively connecting said second lever with said flapper, one of said links being adjustable with respect to one of the levers to change the mechanical advantage therebetween without changing the angularity therebetween to adjust the amount of change in said pneumatic control pressure caused by unit change of the condition-responsive means, and the link connecting said first and second lever hanging substantially vertical and said linkage mechanism being so arranged that the various connections between the links and levers are in contact due to gravity.

5. Means for establishing a pneumatic control pressure responsive to a variable condition comprising, in combination, condition-responsive means, a pilot valve, valve meansresponsive to the operation of said pilot valve for controlling the supply and waste of air from a source to establish said pneumatic control pressure, said pilot valve including a stationary port and a restriction movable with respect thereto, a pneumatic motor operated by said pneumatic control pressure, linkage mechanism including a lever pivotable by said condition-responsive means about an axis movable by said pneumatic motor, normally rigid resilient means connecting said lever with said movable restriction whereby movement of said condition-responsive means and said pneumatic motor each operates said movable restriction to cause said pneumatic control pressure to change'in proportion to movement of the condition-responsive means, and means operated by said condition-responsive means to fiex said normally rigid connecting means to operate directly said movable restricting means independently of said pneumatic motor when said condition-responsive means moves beyond minimum and maximum limits. 7

6. Means for establishing a pneumatic control pressure responsive to a variable condition comprising, in combination, condition-responsive means, a pilot valve, valve; means responsive to the operation of said pilot valve for controlling the supply and waste of air from a source to establish said pneumatic control pressure, said pilot valve including a stationary port and a restriction movable with respect thereto, a pneumatic motor operated by said pneumatic control pressure, linkage mechanism including a lever pivotable by said condition-responsive means about an axis movable by said pneumatic motor, a second lever pivotable about a fixed axis and operatively connected to move said movable restriction, means normally rigid connected to said first and second named levers whereby movement of said condition-responsive means and said pneumatic motor each operates said movable restriction to cause said pneumatic control pressure to change in proportion to movement of the condition-responsive means, a third lever pivotable by said condition-responsive means about an axis concentric with the axis of said second lever and carrying a yoke overlying said second lever, said yoke engaging said second lever to rotate it and flex said normally rigid connecting means when said yoke is moved by said condition-responsive means beyond minimum and maximum limits. g

'7. Means for establishing a pneumatic control pressure responsive to a variable condition comprising, in combination, condition-responsive means, a pilot valve, valve means responsive to the operation of said pilot valve for controlling the-supply and waste of air from a source to establish said pneumatic control pressure, a pneumatic motor comprising opposing bellows interconnected through a restricted passage and having a common movable part and being operated by said pneumatic control pressure, linkage mechanism including a first lever pivoted about and adjustable axis and actuated by said condition-responsive means, a second leverpivoted about an axis carried by said common movable part; a connecting link for transmitting motion of said first lever to said second lever, an operating link for operating said pilot valve from said second lever whereby movement of said condition-responsive means and said common movable part each operates said pilot valve, and one of said links being adjustable with respect to one of the levers to change the mechanical advantage between said link and lever without' changing the efiective angularity therebetween when said movable part and said condition-responsive means are respectively at their neutral positions to adjust the amount of change in the pneumatic control pressure caused by a unit change of the condition-responsive means.

8. Means for establishing a pneumatic control pressure responsive to a variable condition comprising, in combination, condition-responsive means, a pilot valve, valve means responsive to the operation of said pilot valve for controlling the supply and waste of air from a source to establish said pneumatic control pressure, a pneumatic motor operated by said pneumatic control pressure, linkage mechanism including an arm oscillatable about a fixed axis by said conditionresponsive means, a first bell crank movable about an adjustable axis and having a first arm of the same effective length as the oscillatable arm and a link connecting said arms and normally having a right angle relationship with respect to both of said arms, said bell crank having a second arm and a second bell crank movable solely about a third axis movable by said pneumatic motor, a link connecting the last-mentioned arms and slidably adjustable therealong to increase the length of one arm while decreasing the length of the other, and said second bell crank having a second arm for operating said pilot valve, whereby movement of said condition-responsive means and pneumatic motor each operates said pilot valve.

CLESSON E. MASON. 

